Here's the doc string. There is nothing here that tells you the X is across the screen (horizontal) and Y is down the screen (vertical). All it says is that X,Y=0,0 is at the top left.
Yes, you can look up other doc to find out what is meant by position and character cell, but this explanation might as well be self-contained. Return a list (FRAME X . Y) giving the current mouse frame and position. The position is given in character cells, where (0, 0) is the upper-left corner. If Emacs is running on a mouseless terminal or hasn't been programmed to read the mouse position, it returns the selected frame for FRAME and nil for X and Y. If `mouse-position-function' is non-nil, `mouse-position' calls it, passing the normal return value to that function as an argument, and returns whatever that function returns. In GNU Emacs 22.0.50.1 (i386-msvc-nt5.1.2600) of 2006-07-19 on BOS-CTHEWLAP2 X server distributor `Microsoft Corp.', version 5.1.2600 configured using `configure --with-msvc (12.00)' Important settings: value of $LC_ALL: nil value of $LC_COLLATE: nil value of $LC_CTYPE: nil value of $LC_MESSAGES: nil value of $LC_MONETARY: nil value of $LC_NUMERIC: nil value of $LC_TIME: nil value of $LANG: ENU locale-coding-system: cp1252 default-enable-multibyte-characters: t Major mode: Dired by name Minor modes in effect: encoded-kbd-mode: t tooltip-mode: t tool-bar-mode: t mouse-wheel-mode: t menu-bar-mode: t file-name-shadow-mode: t global-font-lock-mode: t font-lock-mode: t blink-cursor-mode: t unify-8859-on-encoding-mode: t utf-translate-cjk-mode: t auto-compression-mode: t line-number-mode: t Recent input: <help-echo> <help-echo> <down-mouse-1> <mouse-1> C-h f m o s <backspace> <backspace> o u s e - p o s i t i o n <return> <help-echo> <help-echo> <help-echo> <help-echo> <menu-bar> <help-menu> <report-emacs-b ug> Recent messages: (C:\Emacs-22-2006-07-19-Fran\bin\emacs.exe -q --no-site-file --debug-init C:\drews-lisp-20) Loading encoded-kb...done For information about the GNU Project and its goals, type C-h C-p. Loading dired... Loading regexp-opt...done Loading dired...done Loading help-fns...done Type C-x 1 to remove help window. Loading emacsbug...done _______________________________________________ emacs-pretest-bug mailing list emacs-pretest-bug@gnu.org http://lists.gnu.org/mailman/listinfo/emacs-pretest-bug